1. Differentiation in the fertility of Inceptisols as related to land use in the upper
Solimões river region, western Amazon*
Fatima Maria de Souza Moreira, Rafaela Simão Abrahão Nóbrega, Ederson da Conceição Jesus,
Daniel Furtado Ferreira, Daniel Vidal Pérez
*Funded by GEF-UNEP, Implemented by TSBF-CIAT
INTRODUCTION MATERIALS AND METHODS
The Upper Solimões river region, western Amazon, is the homeland of In March 2004, 98 composite soil samples had been collected in six windows,
indigenous populations and contains small‐scale agricultural systems that of three different locations: windows 1‐2, in Guanabara II; 3‐5, in Nova Aliança;
are important for biodiversity conservation. Although traditional slash 6, near the town of Benjamin Constant. The sampling comprised six major land
and‐burn agriculture is being practiced over many years, deforestation use systems (LUS). Sampling points (SP) in all windows were distributed in the
there is relatively small compared to other Amazon regions. Pastures are LUS as follows: 30 in Young Secondary Forest, (YSF) 10 in Old Secondary Forest
restricted to the vicinity of cities and do not spread to the small c com‐ (OSF), 17 in Rain Forest (RF), 13 in Pasture (PA), 18 in Agricultures (AGRI) and
munities along the river. Inceptisols are the main soil order (>90%) in the 10 in groforestry (AGRO). Spatially, the sampling points were distributed in a
area and have unique attributes including high Al content and high cation grid with quadrants of 100 x 100 m. Soil samples were collected in the top
exchange capacity (CEC) due to the enrichment of the clay fraction with layer (0‐20 cm). From each composite sample, a sub‐sample was removed, air
2:1 secondary aluminosilicates. Despite its importance, few studies have dried and passed through a 2 mm mesh sieve, and then submitted to analysis.
focused on this soil order when considering land use effects on the fertility Plant‐available P was extracted by Mehlich 1 (HCl 0.05 mol L−1+H2SO4 0.0125
of Amazon soils. mol L−1) and analyzed by spectrophotometry at 660 nm. Soil pH was
measured in a 1:2.5 soil:water suspension. Exchangeable Al, Ca and Mg were
OBJECTIVE extracted with KCl 1 mol L−1. Ca and Mg were determined by atomic
Thus, the objective of this study was to evaluate changes in soil fertility of absorption pectrometry and Al by acid‐base titration. Exchangeable Na and K
representative land use systems (LUSs) in the Upper Solimões region, were extracted with Mehlich 1 and determined by photometry. Potential
namely: primary rainforest, old secondary forest, young secondary forest, acidity (H+Al) was estimated by an equation based on the pH determined in
agroforestry, pasture and agriculture. SMP buffer solution (pH SMP). Organic carbon was determined by oxidation
with dichromate and total N by Kjeldahl. Available micronutrients (Fe, Mn, Zn,
RESULTS and Cu) were extracted by Mehlich 1 and determined by atomic absorption
spectrometry. Boron was extracted with hot water and determined by
spectrophotometry with azomethine‐H at 420 nm. Sulfate was extracted with
Ca(H2PO4)2 0.01 mol L−1 and determined by spectrophotometry at 420 nm.
Dendrogram based on Mahalanobis Linkage distance considering
Biplot of 98 soil samples distributed in 6 windows and comprising 6 land
22 soil chemical and physical variates among land use systems.
use systems in the Western Brazilian Amazon, against values for the first
two principal components, PC1 and PC2, for soil chemical and physical
CONCLUSIONS attributes. Vectors represent edaphic variables that have a high loading
on PC1 and PC2 and that are significant correlated with the ordination
LUSs were significantly differentiated by the chemical attributes of their topsoil (0–20
axes (P<0.05). Each vector points to the direction of increase for a given
cm). Secondary forests presented soil chemical attributes more similar to primary
variable and its length indicates the strength of the correlation between
rainforest areas, while pastures exhibited the highest dissimilarity from all the other
the variable and the ordination scores. Ellipses were arbitrarily added in
LUSs. As a whole, soil chemical changes among Inceptisols dominated LUSs showed
order to help in interpretation and their color refer to the main land use
patterns that were distinct from those reported from other Amazon soils like Oxisols
system included.
and Ultisols. This is probably related to the presence of high‐activity clays enriched in
exchangeable aluminum that heavily influenced the soil chemical reactions over the
expected importance of organic matter found in most studies conducted over Oxisol
ACKNOWLEDGMENTS
and Ultisol.
The authors aknowledge BiosBrasil Technicians Elson Gomes de Souza and Andson Abreu
Magalhães, and the people of the Communities of Nova Aliança and Guanabara 2, for
Science of the Total Environment 408 (2009) 349–355 their major contribution during field work.

2. Phylogenetic relationships among strains isolated from siratro nodules after inoculation of soil samples from diverse land use systems under axenic conditions, based on 16S rDNA sequences and related sequences of β-Proteobacteria. Phylogenies were estimated by the neighbour-joining method. Size of alignment was 537 bp, and gaps were omitted. Bootstrap values were based on 2,000 trials.
Nitrogen‐fixing bacteria communities occurring in soils under different uses
In the Western Amazon region as indicated by nodulation of siratro
(Macroptilium atropurpureum)*
Adriana Silva Lima , Rafaela Simão Abrahão Nóbrega, Alexandre Barberi ,
Krisle da Silva, Daniel Furtado Ferreira , Fatima Maria de Souza Moreira
*Funded by GEF‐UNEP, Implemented by TSBF‐CIAT
INTRODUCTION MATERIALS AND METHODS
Understanding native communities is a crucial step for the management of
biological nitrogen fixation, since they may be either a source of efficient
strains or a limiting factor when efficient strains need to be introduced.
OBJECTIVE Sampling point (SP) geo-referenced
Sub-sample points around SP
This work aimed to evaluate the density, diversity and efficiency of
Leguminosae nodulating bacterial (LNB) communities and their component
strains in soils under various land use systems (LUSs): pristine forest, a Location of Benjamin Constant (BC) Municipality in Brazil. b Location of windows in BC.
agriculture, pasture, agroforestry, young secondary forest, and old c. Distribution of sampling points in window 1 (extracted from Fidalgo et al. 2005). d
secondary forest. The LNB communities were trapped from these soils by Sampling point scheme: one composed soil sample (12 sub‐samples) was collected
using the promiscuous host siratro under controlled conditions. We also around each sampling point
studied their relationships with physical and chemical attributes of the soil.
RESULTS/DISCUSSION
RESULTS/DISCUSSION
Phylogenetic relationships among strains isolated from siratro nodules, based on 16S rDNA
partial sequences and related sequences of α‐Proteobacteria. Phylogenies were estimated
by the neighbour‐joining method. Size of alignment was 386 bp, and gaps were omitted.
Bootstrap values were based on 2,000 trials.
CONCLUSIONS
Agroforestry and agriculture soil samples induced the highest number of nodules in
siratro, while forest soil samples induced the lowest number of nodules. No
relationship was found between LNB and Leguminosae species diversity in the LUSs.
The soil chemical variables that were most related to differences in nodule number
and shoot dry matter weight of plants inoculated with soil suspensions of the LUSs
were, respectively: Ca2+, Mg2+, base saturation, exchangeable bases and Cu2+; and
pH, cation exchange capacity, B, Cu2+ and clay. Although, LNB communities from all Phylogenetic relationships among strains isolated from siratro nodules
LUSs were efficient under controlled and similar conditions, they were found to be based on 16S rDNA sequences and related sequences of β‐Proteobacteria.
composed of strains with variable efficiency: inefficient, efficient, highly efficient and Phylogenies were estimated by the neighbour‐joining method. Size of
superior efficiency. Efficient strains occurred at the highest frequency in all LUSs. The alignment was 537 bp, and gaps were omitted. Bootstrap values
isolated strains presented similar and new sequences that were phylogenetically were based on 2,000 trials.
related to well known LNB genera in α‐and β‐ Proteobacteria. Unusual genera in these Plant Soil (2009) 319:127–145 DOI 10.1007/s11104‐008‐9855‐2
branches, as well as in other branches, which are probably endophytic bacteria, were
also isolated from nodules. These data support siratro as a useful trap species to study ACKNOWLEDGMENTS
the LNB biodiversity of diverse ecosystems in tropical soils. The fact that the highest
diversity and nodulation were seen in managed systems such as agriculture and The authors aknowledge BiosBrasil Technicians Elson Gomes de
agroforestry suggests a high resilience of LNB communities to changes in land use Souza, Andson Abreu Magalhães, and the people of the
after deforestation in a region where large forest areas are still preserved and can be a Communities of Nova Aliança and Guanabara 2, for their major
source of propagules. contribution during field work.